DE10348978A1 - Fuel injection device, in particular for a direct injection internal combustion engine - Google Patents

Abstract

A fuel injection device (18) comprises a housing (28) and two mutually coaxial valve elements (36, 40). Each of these is assigned a fuel outlet opening (62, 90). A biasing device can act on the valve elements (36, 40) in the closing direction. On the valve elements (36, 40) acting in the opening direction of pressure surfaces (52, 80) are present, which each define a pressure chamber (54, 81), which can be connected to a high pressure port (22). It is proposed that the inner valve element (40) comprises at least: a valve body (44), which cooperates with a housing-side valve seat, and a guide body (42), which is guided in the outer valve element (36) and the valve body (44 ) Normally acted upon in the closing direction, wherein between the valve body (44) and the outer valve element (36), a radial gap (71) is present.

Description

The The invention relates to a fuel injection device, in particular for an internal combustion engine with direct injection, with a housing and at least two in the housing arranged and mutually coaxial valve elements, each of which associated with at least one fuel outlet opening, with one of the valve elements acting in the closing direction Biasing device, and each having at least one acting in the opening direction print area at the valve elements, wherein the pressure surfaces each have a pressure chamber limit, which can be connected to a high-pressure connection.

A fuel injection device of the type mentioned is from the DE 40 23 223 A1 known. This shows a fuel injection nozzle with a housing in which two mutually coaxial valve elements are guided. Both valve elements are each assigned a series of fuel outlet openings, and both valve elements are pressed by means of screw compression springs with sealing edges against corresponding housing-side valve seats. In order to open the outer valve element against the force of the compression spring, the pressure in a pressure chamber, which is limited by an acting in the opening direction pressure surface of the outer valve element, increased. As a result, this lifts against the force of the spring from the valve seat, so that fuel can escape through its associated fuel outlet channels. When the outer valve element has lifted, the pressure surface associated with the inner valve element is also subjected to high pressure. Depending on how high the pressure of the fuel is, the inner valve element opens against the force of the compression spring.

such Fuel injectors are also referred to as "coaxial vario nozzles." With they can vary depending on the fuel quantity to be injected Fuel outlet cross-section are provided. This has the advantage that even if only a small amount of fuel to be injected, this are atomized comparatively well can.

The The present invention has the object of a fuel injection device of the aforementioned type so that one with her operated internal combustion engine a particularly good emission behavior shows.

These Task is in a fuel injection device of the aforementioned Sort of solved by in that the inner valve element comprises at least: a valve body which with a housing side Valve seat cooperates, and a guide body, in the outer valve element guided is and the valve body normally in the closing direction acted between between the valve body and the outer valve element a radial gap is present.

Advantages of invention

at the application of the fuel injection device according to the invention in an internal combustion engine, the HC values in the exhaust gas are significantly improved. This depends together with that in the fuel injection device according to the invention reliable prevents the inner valve element from being opened at an opening or closing movement of the outer valve element unintentionally opens and As a result, small amounts of fuel from the fuel injection device escape.

Reached this is achieved by decoupling a part of the inner valve element from the outer valve element: In the fuel injection device according to the invention the inner valve element is divided into a guide body and a valve body. The valve body is that area of the valve element which is connected to the housing side Valve seat works together and ultimately through his movement the flow path of the fuel to the corresponding fuel outlet opens or blocked. Between this valve body and the outer valve element However, a radial gap is present, so that the outer valve element especially during his closing process no lateral forces transferred to this valve body can (the outer valve element touched the valve body the inner valve element so not). These shear forces could too a tilting of the inner valve element and subsequently to a reduced seal between inner valve element and housing lead. Instead is the inner valve element via a Guide body in the outer valve element guided, the valve body in the closing direction applied.

So It may happen that the outer valve element on transverse forces the guiding body of the inner valve member transmits and thereby while closing the outer valve element of Guide body tilted; by decoupling the guide body from valve body However, this is not forwarded to the valve body, so this reliable can remain in the closed position.

It should be noted at this point that the advantages of the invention also in conventional fuel injectors he can be aimed, if only the inner valve member is replaced by the present invention proposed two-part design. As a result, the costs in the production of the fuel injection device according to the invention can be kept low.

advantageous Further developments of the invention are specified in subclaims.

First, will suggested that the guide body a managerial and sealing portion formed in the vicinity of the valve body is and in the outer valve element slidably guided and fluid-tight is. This has the advantage that a the inner valve element associated Dead volume can be kept comparatively small, which increases the precision the injection of fuel by the fuel injection device according to the invention improved, as an unintentional leakage of fuel again can be reduced or even completely avoided. Also the emission behavior is thereby further improved.

alternative but it is also possible that the guide body one managerial and sealing portion which is formed away from the valve body and in the outer valve element slidably guided and fluid-tight is. This corresponds to the embodiment at conventional Fuel injectors, what the realization of the Invention to be made changes reduced and keeps the production costs low.

A particularly advantageous embodiment of the fuel injection device according to the invention is characterized in that in a valve body facing face of the guiding body opens with a leakage connection connected leakage channel. hereby is a "pressure infiltration" avoided. this includes is understood that the area where the guide body and the valve body to each other bump, is subjected to high pressure, whereby a deliberate opening of the inner valve element or the valve body below circumstances prevented or at least delayed would.

In Continuing this is proposed that the leakage channel on his facing away from the valve body Ends in an annulus, formed between the inner and the outer valve member is. It is understood that this annulus on that side of the managerial and sealing portion must be present, which faces away from the fuel outlet channels is. Such a leakage channel can be simple, because this annulus is usually anyway connected to a leakage connection. This keeps the manufacturing costs low.

Further It is suggested that the guide body and the valve body only approximately in a line with a circumferential and radial with respect to the valve body Outside touch lying sealing edge. By such a line contact locally high surface pressure achieved by which a high sealing effect can be realized. As a result, a pressurization of the remote from the valve seat face of the valve body prevents or at least reduces what the functional reliability in particular of the inner valve element increases.

In Further training is proposed that in a guide body facing the end face of the valve body or in a valve body facing end face of the guide body one Recess is present, the radially outer boundary as an annular collar is formed with a peripheral sealing edge. This will the production of the peripheral sealing edge simplifies what the Production costs of the fuel injection device lowers.

A particularly advantageous embodiment of the fuel injection device is also characterized by the fact that the valve body a rounded sealing surface having, which with a housing-side Seat edge cooperates. As a result, so-called "runout tolerances" to a certain extent be compensated, what the production cost and thus the Can reduce manufacturing costs. The "runout tolerances" are angle deviations the contact surface between the valve body and the guide body of one to the longitudinal axis orthogonal plane.

there It is particularly advantageous if this rounded sealing surface a Ring segment of the surface corresponds to a sphere whose center is on the central axis of the inner valve element is located. These in principle of ball joints known configuration allows also during operation an "oblique" arrangement of the valve body without reduction the seal between the valve body and Casing. This can be done during automatically reacts to any resulting angular deviations be without affecting the functionality the fuel injector is impaired.

drawing

following become particularly preferred embodiments the present invention with reference to the accompanying Drawing closer explained. In the drawing show:

1 a schematic representation of a fuel system of an internal combustion engine having a plurality of fuel injection devices;

2 a partially sectioned view of one of the fuel injectors of 1 ;

3 a detailed view III of 2 ;

4a a diagram in which the stroke of an outer valve element of the fuel injection device of 2 is plotted over time;

4b a diagram similar 4a for an inner valve element; and

5 a representation similar 2 an alternative embodiment of a fuel injection device.

description the embodiments

In 1 a fuel system carries the overall reference numeral 10 , It serves to supply an internal combustion engine with fuel, which, however, in 1 not shown in detail.

To the fuel system 10 belongs a reservoir 12 from which a conveyor 14 the fuel to a fuel rail ("Rail") 16 promotes. The conveyor 14 It compresses the fuel to a very high pressure, causing it to be in the fuel rail 16 is stored. The latter are several fuel injectors 18 connected, of which in 1 only two are shown. These inject the fuel in each case in a directly associated combustion chamber 20 the internal combustion engine. The connection of a fuel injection device 18 with the fuel manifold 16 via a high-pressure connection 22 , A leakage connection 24 leads from the fuel injectors 28 via a leakage line 26 to the reservoir 12 back.

The 2 and 3 show one of the fuel injectors 18 more in detail: it includes a housing 28 of which in 2 only a nozzle body 30 and an area of a tail 32 are shown. In the nozzle body 30 is a generally cylindrical and longitudinal recess 34 available. In the upper area is an outer valve element 36 slidably guided and fluid-tight. In the outer valve element 36 is a through hole 38 present, in which an inner valve element 40 is used. This consists of a guide body 42 and a valve body 44 ,

The outer valve element 36 has on its outer circumferential surface on a circumferential shoulder, which acts in an opening direction pressure surface 46 forms. This limits an annular pressure chamber 48 that is in the wall of the recess 34 is formed and via a high-pressure channel 50 with the high pressure connection 22 connected is. At the in the 2 and 3 lower end of the outer valve element 36 is also a pressure acting in the opening direction pressure surface 52 available ( 3 ), which has a pressure room 54 limited, the one between the outer valve element 36 and the wall of the recess 34 formed annulus 56 with the pressure room 48 and thus ultimately with the high-pressure connection 22 connected is. The printing surface 52 becomes radially inward from a sealing edge 58 limited, with an opposite conical seat 60 on the nozzle body 30 exists, works together. The outer valve element 36 is from a compression spring 61 that are on the tail 32 supports, towards the seat 60 applied. The outer valve element 36 is a series of fuel exit channels 62 assigned.

At the guide body 42 of the inner valve element 40 it is an elongate bolt-like part, which has a total of a smaller outer diameter than the inner diameter of the through hole 38 in the outer valve element 36 , At the in 2 lower end of the guide body 42 However, it is a guiding and sealing section 64 present over which the guide body 42 in the outer valve element 36 is guided. The valve body 44 comprises a cylindrical central portion 66 , an adjoining this, rounded tapered sealing section 68 , and a tapered end portion 70 , Between the central section 66 and the recess 38 in the outer valve element 36 is in 3 a radial gap 71 visible, noticeable.

In a guide body 42 facing end face of the central portion 66 is a recess 72 available. Their radially outer boundary is an annular collar 74 with a circumferential sealing edge 76 educated. The sealing edge 76 is in normal operation on a flat end face 78 of the leadership body 42 at. A leakage channel 79 leads from the end face 78 of the leadership body 42 through the guide body 42 obliquely through and opens into a radial wall surface of the guide body 42 , in 2 above the guide and sealing section 64 in one between the guide body 42 and the recess 34 formed annulus 77 , This is ultimately about the leakage connection 24 with the leakage line 26 connected.

The sealing section 68 has a rounded sealing surface 80 on ( 3 ), which corresponds to a ring segment of the surface of a sphere and a pressure space 81 limited. A center 82 this ball lies on a central axis 84 of the inner valve element 40 , The sealing surface 80 of the valve body 44 works with a seat edge 86 together, in the wall of the recess 34 in the nozzle body 30 is trained. The inner valve element 40 is from a compression spring 88 , which are also on the tail 32 supported, against the seat edge 86 applied. The inner valve element 40 is also a series of fuel astrittskanälen 90 assigned.

The fuel injector 18 works as follows:
If only a small amount of fuel is to be injected, it will be connected to the high pressure port 22 a medium pressure applied. This is also in the pressure room 48 and in the pressure room 54 a corresponding pressure on the pressure surfaces 46 and 52 corresponding in the opening direction of the outer valve element 36 produces acting forces. This has the consequence that the outer valve element 36 against the force of the spring 61 opens, that is, the sealing edge 58 from the seat 60 takes off. This allows fuel through the fuel outlet channels 62 flow out.

The pressure, which then also in the pressure room 81 prevails in this case, however, is not sufficient to at the radially outside of the seat edge 86 lying area of the sealing surface 80 of the valve body 44 to generate such force acting in the opening direction that the inner valve element 40 against the force of the spring 88 opens. From the fuel outlet channels 90 thus no fuel can escape. Because of the valve body 44 from the outer valve element 36 is not touched (gap 71 ), this can neither during the opening process nor during the closing process, lateral forces on the valve body 44 transfer. The outer valve element 36 Therefore, no tilting movement in the valve body 44 induce through which the sealing surface 80 at least partially from the seat edge 86 take off and thus lead to the exit of a small amount of fuel.

By decoupling the valve body 44 from the outer valve element 36 Thus, it is effectively prevented that during the opening operation of the outer valve element 36 or / and during the subsequent closing procedure (when the pressure at the high-pressure connection 22 is lowered again) fuel from the fuel outlet channels 90 unintentionally exits. This also results from the 4a and 4b : In 4a is the stroke of the outer valve element 36 shown in 4b the stroke of the valve body 44 , each one at the high-pressure connection 22 applied mean fuel pressure. It can be seen that the position of the valve body 44 during opening and during closing of the outer valve element 36 is not affected.

If a larger amount of fuel to be injected, is at the high pressure port 22 a corresponding high fuel pressure applied. This is so high that after opening the outer valve element 36 the then also in the pressure room 81 ruling and at the sealing surface 80 applied pressure sufficient to the inner valve element 40 against the force of the spring 88 to open. Fuel can now pass through both rows of fuel exit channels 62 and 90 escape.

Through the sealing edge 76 Effectively prevents high pressure fuel from passing through the gap 71 into the recess 72 get there and there in the closing direction of the valve body 44 can produce acting force. This could be the safe opening of the valve body 44 affect. In addition, it is still in the recess 72 entering fuel through the leakage channel 79 to the leakage connection 24 dissipated.

An alternative embodiment of a fuel injection device 18 is in 5 shown. In this case, bear such elements and areas, which have equivalent functions to elements and areas of the preceding figures, the same reference numerals. A major difference in 5 shown fuel injector 18 to that of 2 relates to the arrangement of the guide and sealing section 64 on the outer valve element 36 :
While at the in 2 shown embodiment of the guide and sealing section 64 at the lower end of the outer valve element in the figure there 36 is arranged, he is at the in 5 shown embodiment at the upper end, ie from the valve body 44 removed, arranged. Accordingly, the leakage channel leads 79 not oblique, but coaxial with the outer valve element 36 through this and is only above the guide and sealing section 64 in an intermediate piece 92 led outwards diagonally.

Claims (9)

Fuel injection device ( 18 ), in particular for a direct injection internal combustion engine, with a housing ( 28 ) and at least two in the housing ( 28 ) and mutually coaxial valve elements ( 36 . 40 ), each having at least one fuel outlet opening ( 62 . 90 ), with one of the valve elements ( 36 . 40 ) acting in the closing direction biasing device ( 61 . 88 ), and each having at least one pressure surface acting in the opening direction ( 46 . 52 . 80 ) on the valve elements ( 36 . 40 ), the pressure surfaces ( 36 . 52 . 80 ) each have a pressure chamber ( 48 . 54 . 81 ) with a high-pressure connection ( 22 ), characterized in that the inner valve element ( 40 ) at least comprises: a valve body ( 44 ) fitted with a housing-side valve seat ( 86 ) and a management body ( 42 ), which in the outer valve element ( 36 ) is guided and the the valve body ( 44 ) normally acted in the closing direction, wherein between the valve body ( 44 ) and the outer valve element ( 36 ) a radial gap ( 71 ) is available. Fuel injection device ( 18 ) according to claim 1, characterized in that the guide body ( 42 ) a guide and sealing section ( 64 ), which in the vicinity of the valve body ( 44 ) is formed and in the outer valve element ( 36 ) is guided sliding and fluid-tight. Fuel injection device ( 18 ) according to claim 1, characterized in that the guide body ( 42 ) a guide and sealing section ( 64 ), which of the valve body ( 44 ) is formed remotely and in the outer valve element ( 36 ) is guided sliding and fluid-tight. Fuel injection device ( 18 ) according to any one of the preceding claims, characterized in that in a the valve body ( 44 ) facing end face ( 78 ) of the guiding body ( 42 ) with a leakage connection ( 24 ) connected leakage channel ( 79 ) opens. Fuel injection device ( 18 ) according to claim 4, characterized in that the leakage channel ( 79 ) at its from the valve body ( 44 ) facing away from the end in an annular space ( 77 ), which between the inner valve element ( 40 ) and the outer valve element ( 36 ) is trained. Fuel injection device ( 18 ) according to one of the preceding claims, characterized in that the guide body ( 42 ) and the valve body ( 44 ) only linearly with a circumferential and with respect to the valve body ( 42 ) radially outer sealing edge ( 86 ) touch. Fuel injection device ( 18 ) according to claim 6, characterized in that in a the guide body ( 42 ) facing end face of the valve body ( 44 ) or in a valve body facing the end face of the guide body has a recess ( 72 ) is present, whose radially outer boundary as an annular collar ( 74 ) with a circumferential sealing edge ( 76 ) is trained. Fuel injection device ( 18 ) according to one of the preceding claims, characterized in that the valve body ( 44 ) a rounded sealing surface ( 80 ), which with a housing-side seat edge ( 80 ) works together. Fuel injection device ( 18 ) according to claim 8, characterized in that the rounded sealing surface ( 80 ) corresponds to a ring segment of the surface of a sphere whose center ( 82 ) on the central axis ( 84 ) of the inner valve element ( 40 ) lies.